package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import org.apache.lucene.index.IndexReader;

/** 
 * Constrains search results to only match those which also match a provided
 * query.  
 *
 * <p> This could be used, for example, with a {@link TermRangeQuery} on a suitably
 * formatted date field to implement date filtering.  One could re-use a single
 * QueryFilter that matches, e.g., only documents modified within the last
 * week.  The QueryFilter and TermRangeQuery would only need to be reconstructed
 * once per day.
 */
public class QueryWrapperFilter extends Filter {
    private Query query;

    /** Constructs a filter which only matches documents matching
     * <code>query</code>.
     */
    public QueryWrapperFilter(Query query) {
        this.query = query;
    }

    @Override
    public DocIdSet getDocIdSet(final IndexReader reader) throws IOException {
        final Weight weight = new IndexSearcher(reader).createNormalizedWeight(query);
        return new DocIdSet() {
            @Override
            public DocIdSetIterator iterator() throws IOException {
                return weight.scorer(reader, true, false);
            }

            @Override
            public boolean isCacheable() {
                return false;
            }
        };
    }

    @Override
    public String toString() {
        return "QueryWrapperFilter(" + query + ")";
    }

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof QueryWrapperFilter))
            return false;
        return this.query.equals(((QueryWrapperFilter) o).query);
    }

    @Override
    public int hashCode() {
        return query.hashCode() ^ 0x923F64B9;
    }
}
